1. Field of the Invention
The present invention relates to a control signal generating circuit suitable for use with a display apparatus or the like in which a picture screen, for example, is divided into a plurality of areas and images of different picture qualities are displayed in these areas. More particularly, the present invention relates to a control signal generating circuit in which, when a picture quality of every area is improved by using a marker signal, the marker signal can be made inconspicuous.
2. Description of the Related Art
In a display apparatus such as a television receiver for displaying a video signal based on a television broadcasting and a video signal played back from a video tape or the like, for example, in order to improve a display picture quality of a still picture represented by a photographic picture or the like and a moving picture represented by a motion picture or the like, there have heretofore been implemented picture quality improvement techniques such as enlarging a brightness difference (hereinafter referred to as a contrast ratio) between a white level and a black level of displayed picture by increasing an amplifying ratio of a video signal, for example, or emphasizing a contour of a picture (hereafter referred to as a sharpness).
There have been realized a variety of semiconductor integrated circuits (hereinafter referred to as ICs) having more than one such picture quality improvement function to improve these picture quality improvement functions by control means using a direct current voltage (hereinafter referred to as a DC voltage) from the outside, for example, or information transmission means such as a so-called bus communication and so on. As representing examples of such semiconductor integrated circuit, there are known a preamplifier IC for use in a video amplifying circuit, for example, an RGB decode IC for decoding luminance/color difference signals to provide red/green/blue signals or the like.
By the way, in a monitor display apparatus for displaying an output of a computer, for example, it has been a main purpose to display information of characters, digital numbers and so on of document and spreadsheet or the like outputted from a computer. Therefore, the monitor display apparatus is generally used in order to display an image signal supplied from a computer in the form of a binary signal of "1/0", for example, at a proper luminance level.
On the other hand, in a computer having multimedia capabilities, not only information of the above-mentioned characters and digital number but also images of photographs, and moving pictures and the like from a disk apparatus and a video card had heretofore been displayed in an arbitrary range called a window. In that case, since the images of photographs, moving pictures and so on thus taken into the computer are low in contrast and sharpness as compared with information such as characters, digital numbers and the like, when they are displayed together with such information, picture qualities of photograph and moving picture or the like are deteriorated considerably.
Therefore, in such monitor display apparatus, in order to improve picture qualities of images of photograph and moving picture or the like, it has been considered to improve the above-mentioned contrast ratio and sharpness.
However, in the conventional monitor display apparatus, it is unavoidable that such picture quality improvement such as enlargement of the above-mentioned luminance difference, the contour emphasis and so on is uniformly effected on the whole of the picture screen. As a result, when the picture screen has therein the display areas of characters and digital numbers or the like, there is then the risk that these displayed characters and digital numbers or the like become difficult to read. In particular, when displayed characters and digital numbers or the like are too high in brightness, user's eyes tire easily.
Also, recently, as so-called internet have been developed and a text broadcasting is widespread, increasing an opportunity at which general television receivers display images of photograph and moving pictures or the like and characters and digital numbers or the like on one picture screen. Accordingly, also in such a television receiver, when such picture quality improvement such as enlargement of the above-mentioned luminance difference and the contour emphasis or the like is uniformly effected on the whole of the picture screen, there is then the risk that these characters and digital numbers displayed on the picture screen become difficult to read.
On the other hand, the inventors of this application have previously proposed a display apparatus (PCT application No. JP98/04747) in which a marker signal comprised of combinations of arbitrary patterns of primary colors of predetermined levels is formed in a video signal, this marker signal is detected and different image processing is effected at every detected area.
That is, as shown in FIG. 9, red/green/blue video signals (R/G/B) inputted to input terminals 1R, 1G, 1B are respectively supplied through capacitors 2R, 2G, 2B to a preamplifier IC 3. In this preamplifier IC 3, the supplied video signals (R/G/B) are respectively supplied through clamping circuits 31R, 31G, 31B to sharpness improvement circuits 32R, 32G, 32B, which will be described later on, and further outputted through amplifiers 33R, 33G, 33B which will be described later on.
The video signals (R/G/B) outputted from this preamplifier IC 3 are amplified by an output amplifier 4 and then outputted through capacitors 5R, 5G, 5B. Further, these video signals (R/G/B) thus outputted are DC-voltage-converted by a cutoff adjustment amplifier 6 and then supplied to a cathode-ray tube (hereinafter referred to as a CRT)7, for example, serving as a display means, thereby resulting in an image based on picture-quality-improved video signals (R/G/B), which will be described later on, being displayed on the screen of the CRT 7.
A microcomputer (hereinafter referred to as a microcomputer: although not shown) exiting within this apparatus and which controls a variety of functions is adapted to generate data of first and second DC voltages for controlling the above-mentioned sharpness and data of first and second DC voltages for controlling the contrast ratio, for example. Further, the data thus generated are supplied to D/A-converting (hereinafter referred to as a DAC) circuits 34A and 34B; and 35A and 35B, in which they are respectively converted into control DC voltages.
The control DC voltages thus converted by these DAC circuits 34A and 34B; and 35A and 35B are selected by switch circuits 36, 37 and then supplied to the above-mentioned preamplifier IC 3. Thus, the preamplifier IC 3 controls the above-mentioned sharpness improvement circuits 32R, 32G, 32B and the above-mentioned amplifiers 33R, 33G, 33B in accordance with the supplied control DC voltages, thereby resulting in the sharpness and the contrast ratio being improved.
Further, in this apparatus, video signals (R/G/B) upon which marker signals for designating arbitrary areas of the picture screen from, for example, an outside computer (not shown) are superimposed are supplied to the input terminals 1R, 1G, 1B. Here, the marker signals are comprised of arbitrary signal patterns, respectively, and signal patterns 101a, 101b, 102a, 102b comprising these arbitrary marker signals are respectively provided at four corners of an area 100 to be detected as shown in FIG. 10, for example.
Accordingly, in the apparatus shown in FIG. 9, the video signals from the above-mentioned input terminals 1R, 1G are supplied through amplifiers 8R, 8G to input terminals of shift registers 9R, 9G, and the video signal from the input terminal 1B is supplied through a comparator 8B to clock terminals of the shift registers 9R, 9G. The signals thus accumulated in these shift registers 9R, 9G are supplied to a comparator 10C, in which they are compared with a signal pattern 101 or 102 stored in a memory 10M, for example.
Therefore, there are detected the above-mentioned signal patterns 101a, 101b, 102a, 102b. That is, in these signal patterns, as shown in FIG. 11, for example, using the blue (B) signal of the video signal, for example, as a clock, red (R) and blue (B) signals constitute a marker signal. Then, at the timing of the leading edge (trailing edge of the inverted signal) of the blue (B) signal, the patterns of the red (R) and green (G) signals are latched in the above-mentioned shift registers 9R, 9G, for example.
In the illustrated example,for example, a pattern of (1011) is latched in the shift register 9R, and a pattern of (0111) is latched in the shift register 9G. Further, these patterns are compared with the patterns stored in the memory 10M and thereby the signals patterns 101, 102 which become arbitrary marker signal are detected. Incidentally, the arrangement of the illustrated signals is described by way of example, and it is needless to say that various kinds of signal patterns can be generated by changing the above-mentioned patterns or by increasing or decreasing the number of bits or the like.
Also, a horizontal synchronizing signal from an input terminal 11H is supplied to a PLL (Phase-Locked Loop )circuit 12. An oscillation signal from an oscillator 13 is supplied to this PLL circuit 12 which then generates an arbitrary clock signal synchronized with the horizontal synchronizing signal. This clock signal is supplied to a count terminal of a horizontal counter 14H, and a horizontal synchronizing signal or a signal synchronized with the horizontal synchronizing signal is supplied to a reset terminal. Thus, this horizontal counter 14H outputs a count value corresponding to the horizontal position on the display screen.
Further, the horizontal synchronizing signal is supplied to a count terminal of a vertical counter 14V, and a vertical synchronizing signal from an input terminal 11V or a signal synchronized with the vertical synchronizing signal is supplied to a reset terminal. Thus, this vertical counter 14V outputs a count value corresponding to a vertical position (scanning line) on the display screen. The count values of these horizontal counter 14H and vertical counter 14V are supplied to latch circuits 15A, 15B and 16A, 16B, respectively.
Detection signals of the signal patterns 101, 102 detected by the above-mentioned comparator 10C are supplied to trigger terminals of latch circuits 15A, 16A and 15B, 16B, respectively. Thus, the latch circuit 15A latches the count value corresponding to the horizontal position of the signal pattern 101a or 101b on the display screen, for example. Also, the latch circuit 15B latches the count value corresponding to the horizontal position of the signal pattern 102a or 102b on the display screen, for example.
Further, the latch circuit 16A latches the count value corresponding to the vertical position of the signal pattern 101a or 102a on the display screen, for example. Also, the latch circuit 16B latches the count value corresponding to the vertical position of the signal pattern 101b or 102b on the display screen, for example.
Then, the signals latched in these latch circuits 15A, 15B and 16A, 16B are supplied to comparators 17A, 17B and 18A, 18B, respectively, and the count values of the above-mentioned horizontal counter 14H and vertical counter 14V are supplied to the comparators 17A, 17B and 18A, 18B, respectively.
Thus, the comparator 17A outputs a signal when the count value of the horizontal counter 14H agrees with the count value of the horizontal position of the signal pattern 101a or 101b latched in the latch circuit 15A. Also, the comparator 17B outputs a signal when the count value of the horizontal counter 14H agrees with the count value of the horizontal position of the signal pattern 102a or 102b latched in the latch circuit 15B.
Further, the comparator 18A outputs a signal when the count value of the vertical counter 14V agrees with the count value of the vertical position of the signal pattern 101a or 102a latched in the latch circuit 16A. Also, the comparator 18B outputs a signal when the count value of the vertical counter 14V agrees with the count value of the vertical position of the signal pattern 101b or 102b latched in the latch circuit 16B.
Then, the signals from these comparators 17A and 17B are supplied to set and reset terminals of a flip-flop 19H, thereby resulting in a pulse signal corresponding to a width of a horizontal direction of the area 100 shown at B in FIG. 10 being outputted. Also, the signals from the comparators 18A and 18B are supplied to set and reset terminals of a flip-flop 19V, thereby resulting in a pulse signal corresponding to a width of a vertical direction of the area 100 shown at C in FIG. 10 being outputted.
Further, signals from these flip-flops 19H and 19V are synthesized by a multiplier 20 and thereby a control signal shown at D in FIG. 10 is generated. Then, this control signal is supplied to the above-mentioned switch circuits 36, 37, whereby the control DC voltages converted by the DAC circuits 34A or 34B, and 35A or 35B are selected.
Thus, of the image displayed on the above-mentioned CRT 7, the sharpness and the contrast ratio of the image in the arbitrary area designated by the above-mentioned control signal are changed. That is, it is possible to increase the sharpness and the contrast ratio of only the area 100 of the image such as a photograph and a moving picture or the like captured in a display screen. Thus, a picture quality of an image such as captured photograph and moving picture or the like can be improved. Incidentally, the picture quality can also be improved by other suitable methods such as a gamma correction, a color correction and the like.
However, in this apparatus, the signal patterns 101a, 101b, 102a, 102b comprising the above-mentioned marker signals are determined irrespective of the original superimposed video signal. As a result, if the signal patterns have luminance and hue differences between them and the original video signal, then there is a fear that the signal patterns 101a, 101b, 102a, 102b become conspicuous on the displayed picture.
That is, the signal patterns 101a, 101b, 102a, 102b comprising the marker signals are superimposed upon the original video signal at a very high level in order to make the detection of the marker signal become reliable. Further, since these signal patterns are comprised of combinations of primary colors, they become conspicuous in the image such as the photograph and the moving picture or the like displayed on the area 100, for example. As a result, these signal patterns become offensive to the eye, and become factors for remarkably degrading commerciality of a product on which such processing is effected.
In view of the aforesaid aspect, the present application is made, and the problem to be solved is that, in the conventional apparatus, the signal patterns comprising the marker signals become conspicuous on the displayed picture and the superimposed signal patterns become offensive to the eye, thereby resulting in commerciality of the product on which such processing is effected being degraded.